Optical remote sensing devices are widely used in both commercial and military applications. Many applications involve long range tracking and aiming, and as a result, require a high level of magnification, or zoom, in the optics. Tracking small objects, such as vehicles or people, from long range is difficult because the high zoom of the tracking optics required to see the object necessitates a narrow field of view. As a result of the narrow field of view, it is difficult to reacquire the object if it is lost due to terrain, shadows, or other phenomena. Furthermore, pure optical tracking of vehicles or other relatively small objects is severely impeded by the presence of tree canopies, shadows, and urban terrain which may obscure the object.
Traditional approaches to addressing these issues have involved the use of variable zoom optics and systems with sophisticated tracking algorithms. However, such systems suffer from several disadvantages and are only somewhat effective. For example, there is a time delay associated with changing the zoom, during which time the target object may move outside of the field of view. Also, in certain systems the optics are not focused during the zooming action, and therefore the target object may not be visible during the zoom and may be lost as a result. Additionally, the moving parts associated with most traditional variable zoom optics are common points of failure in the system. Sophisticated LIDAR ranging techniques have been developed to attempt to located objects below tree canopies, for example, by looking for the object through the tiny openings between leaves; however, traditional systems are complicated and expensive. Accordingly, there exists a need for a simple, robust optical system capable of performing long range tracking of relatively small objects, such as vehicles.